System and method for determining reticle defect printability

ABSTRACT

A method and software program for determining printability of a defect on a reticle or photomask onto a substrate during processing. That is performed by creating a pixel grid image having a plurality of individual pixel images showing the defect. A gray scale value is assigned to each pixel image of the pixel grid image and a probable center pixel of the defect is selected. Then the polarity of the defect is determined, with a coarse center pixel of the defect optionally selected using the probable center defect and polarity of the defect. If a coarse center pixel is selected, then a fine center of the defect can optionally be selected from the coarse center pixel and polarity of the defect. From the center pixel the physical extent of the defect can be determined followed by the determination the transmissivity energy level of the physical extent of the defect. Optionally, the proximity of the defect to a pattern edge on the reticle or photomask can be determined using the physical extent and polarity of the defect. Then the printability of the defect can be determined from the transmissivity energy level of the defect and characteristics of the wafer fabrication process being used to produce the substrate from the reticle or photomask.

FIELD OF THE INVENTION

[0001] The present invention relates generally to electro-opticalinspection systems, and more particularly to an automated reticleinspection system and method for determining which defects in a reticlewill print on the substrate and effect the performance of a completedsemiconductor device.

BACKGROUND OF THE INVENTION

[0002] Present reticle and photomask inspection systems currentlyidentify defects on reticles and photomasks merely as defective pixels.No effort is made to determine printability and the ultimate impact ofidentified defects on a finalized semiconductor device. That approachhas been satisfactory in the past given the trace widths and number ofcomponents to be implemented on a single substrate and in a single chip.

[0003] However new technology has continued to push the line andcomponent density on a single semiconductor substrate, and in a singlechip, to greater and greater levels with ever narrower line widths beingrequired. That being true, and given the previous criteria as to whatdefects are a potential problem, smaller and smaller anomalies inreticles and photomasks are being considered a defect. Given the currenttechnology, anomalies of well below one micron in size (down to 200nanometers in some cases) are being considered defects. Therefore,inspection machines have been refined to detect these ever smalleranomalies on reticles and photomasks.

[0004] Currently, in the semiconductor industry, complex reticles andphotomasks that can cost tens of thousands of dollars to produce arebeing scraped since it is believed that even the smallest defect in onereticle or photomask used in the production of a substrate may have adetrimental effect on the performance of the final semiconductorcomponent.

[0005] What is needed is a method and system that not only identifiesthe ever smaller anomalies on a reticle or photomask as a defect, butwhich goes further and considers other characteristics, the location ofthe defect, and the line patterns on the reticle or photomask, todetermine whether or not each individually identified defective pixelwill print onto the semiconductor substrate. If this is accomplished,many reticles and photomasks that are currently being scraped couldinstead be used with no detrimental effect on the operation of the finalsemiconductor component, thus reducing the cost of production ofsemiconductor devices. It is believed that the present inventionprovides that capacity.

SUMMARY OF THE INVENTION

[0006] The present invention includes a method and software program fordetermining printability of a defect on a reticle or photomask onto asubstrate during processing. That is performed by creating a pixel gridimage having a plurality of individual pixel images showing the defect.A gray scale value is assigned to each pixel image of the pixel gridimage and a probable center pixel of the defect is selected. Then thepolarity of the defect is determined, with a coarse center pixel of thedefect optionally selected using the probable center defect and polarityof the defect. If a coarse center pixel is selected, then a fine centerof the defect can optionally be selected from the coarse center pixeland polarity of the defect. From the center pixel the physical extent ofthe defect can be determined followed by the determination thetransmissivity energy level of the physical extent of the defect.Optionally, the proximity of the defect to a pattern edge on the reticleor photomask can be determined using the physical extent and polarity ofthe defect. Then the printability of the defect can be determined fromthe transmissivity energy level of the defect and characteristics of thewafer fabrication process being used to produce the substrate from thereticle or photomask.

DESCRIPTION OF THE FIGURES

[0007]FIG. 1 is a general flow diagram that illustrates the steps of thepresent invention.

[0008]FIG. 2 illustrates a 256 by 256 pixel grid image that is used bythe present invention as a general work area for the present invention,and here illustrates the determination of the polarity of a defect.

[0009]FIG. 3 illustrate a 3 by 3 pixel window that is used to determinethe coarse center pixel.

[0010]FIG. 4 illustrates a subpixel peak gray scale value locationroutine to prform a fine location of the center of a defect.

[0011]FIG. 5 is a representative gray scale value variation for a pixelof a defect along one axis with reference to the spacing between thecenter pixel of the defect to those pixels extending away from thecenter pixel.

[0012]FIG. 6 illustrates the determined extent of a defect in the pixelgrid image and adjacent groupings of pixels in the same size and shapeas the extent of the defect.

[0013]FIG. 7a illustrates a typical gray scale value variation for thepixels adjacent to each side of, and those that make up the edge of, aline on a reticle.

[0014]FIG. 7b illustrates the use of linear sub-pixel interpolation tolocate the edge of a line on a reticle.

[0015]FIG. 8 is a simplified functional block diagram of a prior artmask inspection system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

[0016] There are numerous inspection machines available that have thecapability of identifying defects on a reticle or photomask. An exampleof such a machine that performs the inspection automatically by eitherdie-to-die or die-to-database inspection is described in detail inEuropean Patent Specification EP 0532927B1 published Feb. 21, 1996,entitled “Automated photomask inspection apparatus”, and which isincorporated herein by reference. In performing that inspection, theabove identified inspection machine, and other similar machines, scansthe reticle or photomask and pixelizes the image, saving the pixellocation information for each of the scanned regions where there is notagreement between the dies (in die-to-die) or between the die and thedata base (in die-to-data base). A typical pixel size used by suchinspection machines is a 0.25 μm square. What is not determined by thecurrently available defect detection machines is the transmittibleenergy level of light through the groups of pixels that constitute eachdefect; more specifically the transmittible energy level of theradiation frequency used by the steeper to expose a semiconductor waferto the pattern on the reticle or photomask prior to each chemicalprocessing step of the wafer in the production of the finishedsemiconductor component.

[0017] It has been discovered that there are numerous factors thatcontribute to whether or not a defect on a reticle or photomask willprint on a substrate. The size of such a defect is only one of thosefactors. It has also been determined that the energy level that willpass through such a defect is equally important to being able to make adetermination as to whether or not such a defect will print onto asubstrate that is exposed to such a reticle or photomask. There arestill other factors that contribute to whether or not such a defect willprint onto a substrate.

[0018] The primary factor as to the printing of a defect in a reticle ona substrate is the transmittible energy level through that defect. It isclear that if the defect in question is a type that is not transmissive,there can be no trace of that defect on the substrate exposed by thereticle in which the defect is contained, regardless of the size of thatdefect.

[0019] There are numerous other factors that influence whether or not adefect prints onto a substrate. Those include, among other factors, thetype of resist used on the substrate, line width size, stepper type,numerical aperture of the stepper, focus of the stepper, radiationfrequency of the stepper, exposure time of the stepper, etc.

[0020] Referring to FIG. 1, the actual process of the present inventionthus begins with the defect review menu (10) that the prior artinspection machine creates. A microscope is then used, by an operator orautomatically, to capture the image of a defect (12) from the defectreview menu by scanning that defect image and creating a pixel gridimage (e.g., 256 by 256 pixels with the pixel size being 0.25 μm) of adefective area. Then, using a gray scale resolution of 256 levels, eachpixel in that captured image is digitized (14) by assigning a gray scalevalue that corresponds to the brightness or darkness of that pixel from0 to 256, with 0 being for opaque pixels and 256 being for fullytransmissive pixels of the defective area of the photomask. FIG. 8 is aprior art mask inspection system (FIG. 1 of European PatentSpecification EP 0532927B1) that could be used to perform this functionwith optical subsystem 116 acting as the microscope, and delivering theimage from the reticle 114 to electronic subsystem 120, all under thecontrol of control computer 124.

[0021] More specifically, the simplified block diagram of FIG. 8 is of aprior art mask inspection system 110 that includes a stage 112 forcarrying a substrate 114 to be inspected, an optical subsystem 116, adata base adaptor 218, an electronics subsystem 120, a display 122, acontrol computer 124, and a keyboard 126. The stage 112 is a precisiondevice driver under control of subsystem 120 and capable of moving thesubstrate 114 under the test relative to the optical axes of the opticalsubsystem 116 so that all or any selected part of the substrate surfacemay be inspected. Optical subsystem 116 includes a light source 130 andrelated optics which cause a beam of light to be deflected back andforth over a small angle as viewed by the substrate 114. The light beamemitted by light 130 is deflected by the combination of twoacousto-optic elements; an acousto-optic prescanner 140 and anacousto-optic scanner 142. When the light beam emerges from the scanner142 it 25 then enters a cube beam splitter 160. The beam next passesthrough an objective lens 182 which focuses the beam onto the substrate114. Light passing through the substrate 114 is then collected by acondenser lens 184 and focused onto the transmission detector 134.

[0022] With a gray scale value assigned to each pixel in the defectarea, the probable center of the defect is selected (16) and thecoordinates of the pixel at that location are noted. Next the polarity(white or black) of the defect is determined (18) by comparing the grayscale value of the pixel at the selected probable center of the defectto the gray scale value of at least one reference pixel a number ofpixels spaced apart from the probable center pixel (e.g., 10 pixels tothe right). If the gray scale value of the selected probable centerpixel is less than the gray scale value of the reference pixel, thedefect is considered to be black, or have negative energy. If the grayscale value of the selected probable center pixel is greater than thegray scale value of the reference pixel, the defect is considered to bewhite, or have positive energy.

[0023] Alternatively, reference pixels 2, 5, 7 and 10 pixel positionsaway from the probable center pixel could each be checked and if grayscale value successively from reference pixel to reference pixelcontinues to drop then the defect is considered to be white, or havepositive energy. Whereas, if the gray scale values successively fromreference pixel to reference pixel continues to rise then the defect isconsidered to be black, or have negative energy. However, if the grayscale value of the reference pixels at first moves in one direction andthen changes direction the further that reference pixel is from theprobable center pixel, the probable center pixel is near a line edge andthe reference pixel progression will have to be performed in anotherdirection without encountering a line edge.

[0024]FIG. 2 illustrates a pixel grid image 34 as discussed above withrespect to blocks 12 and 14 above. Additionally, there is shown aprobable center pixel 36 of that image and a single reference pixel 38that is used as discussed above with respect to blocks 16 and 18 todetermine the polarity of the defect. Alternatively, FIG. 2 also shows aprobable center pixel 36′ and reference pixels 38 ², 38 ⁵, 38 ⁷ and 38¹⁰, as discussed in the alternative approach that avoids making thedecision when there is a line edge in close proximity to the probablecenter pixel.

[0025] This procedure to identify the defect as either black or whitecould be refined further by considering a second reference pixel eitherfurther away from the selected probable center pixel, or in anotherdirection than the first reference pixel, if the gray scale differencesbetween the first considered reference pixe; and the selected probablecenter pixel are closer together than a preselected difference. Stillother distances and directions could be tried until a more definitivevalue difference is observed to better determine the polarity of thedefect.

[0026] Referring again to FIG. 1, with the polarity of the defectdetermined, a coarse center of the defect (20) is determined by findingthe pixel in the defect with the minimum or maximum (according to thepolarity) gray scale value. This is accomplished by comparing the grayscale values of the pixels in a square pixel window around the selectedcoarse center pixel (e.g., 3 by 3 pixels with the selected coarse centerpixel in the center). If the gray scale value of one of those pixels incomparison with the selected pixel is determined to be higher (whitepolarity defect), or lower (black polarity defect), that pixel isselected as the new coarse center pixel and a second pixel window of thesame size, centered about the new coarse center pixel, is observed andthe search is performed again. This process can be repeated as manytimes as necessary to find a better choice of the coarse center pixel ofthe defect. To insure accuracy this test can be repeated at least someminimum number of times, perhaps 5, to fully search for and identify thebest coarse center pixel.

[0027]FIG. 3 illustrates the use of a square pixel window 40 of the typedescribed above with respect to block 20 of FIG. 1. Here, for the firststep at the determination of the coarse center pixel with the probablecenter pixel 36 first selected as the coarse center pixel with the firstsquare 3 by 3 pixel window 40 drawn around it. In each of the squares ofwindow 40 a representative gray scale value has been shown with 76having been assigned to pixel 36. Then, the gray scale value of each ofthe surrounding pixels is compared to the value of pixel 36 to determineif there is a pixel that has a gray scale value that is higher than thatof pixel 36. In this example it can be seen that pixel 42 has a grayscale value that is 79 versus the 76 of pixel 36, thus pixel 42 isselected as the next coarse center pixel. Again a 3 by 3 pixel window 44is drawn around pixel 42 and the surrounding gray scale values of thosepixels are compared to the gray scale value of pixel 42 in search ofanother pixel with a higher gray scale value. In this example, pixel 42has the highest gray scale value and therefore would be selected as thecoarse center pixel of the defect.

[0028] Returning again to FIG. 1, with the coarse center pixel of thedefect determined, the subpixel center of the defect can be more finelydetermined (22) by using a subpixel interpolation routine. Using thegray scale values for the best coarse center pixel, and surroundingpixels (e.g., the pixel on either side of the coarse center pixel ineach direction of interest—x, y and diagonals perhaps), a fineapproximation of the defect center, to within less than a pixeldimension (e.g., to within 0.1 pixels) can be determined.

[0029]FIG. 4 shows an example of a subpixel interpolation routine in onedirection. Here, the gray scale level variation versus distance for arepresentative defect is shown with the location and gray scale valuesof the coarse center pixel 42 (here numbered 2) and the nearest pixelson opposite sides thereof along the same axis (here numbered 1 and 3,respectively). Also, for purposes of this illustration, pixels 1, 2 and3 each has a gray scale value of 60, 80 and 75, respectively. Also fromthe defect gray scale curve it can be seen that coarse center pixel 42is not quite at the peak gray scale value of the defect along therepresentative axis. The fine center of the defect can be located withthe following formula: $\begin{matrix}{{{fine}\quad {pixel}\quad {center}} = \frac{x_{1} + {2( x_{2} )} + {3( x_{3} )}}{x_{1} + x_{2} + x_{3}}} & (1)\end{matrix}$

[0030] where x₁ is the gray scale value of pixel 1;

[0031] x₂ is the gray scale value of pixel 2; and

[0032] x₃ is the gray scale value of pixel 3.

[0033] Using the sample gray scale values of FIG. 4a, equation (1)yields: $\begin{matrix}{{{fine}\quad {pixel}\quad {center}} = {\frac{60 + {2(80)} + {3(75)}}{60 + 80 + 75} = \frac{60 + 160 + 150}{215}}} \\{= {\frac{445}{215} = 2.0697}}\end{matrix}$

[0034] thus the fine center pixel location is 0.0697 of a pixel widthcloser to pixel 3 from pixel 2, or 6.97% of a pixel width from thecenter of pixel 2 in the direction of pixel 3.

[0035] Again returning to FIG. 1, with the center of the defectdetermined, the size of the defect, or physical extent of the defect inseveral directions (24), can next be determined. This is accomplished byfirst noting the gray scale value of the pixel at the center of thedefect. That gray scale value is then compared to the gray scale valueof the next adjacent pixel in a selected direction. If the difference ingray scale values is greater than a preselected level (e.g., 2), thepixel location is incremented in the same direction by one with the grayscale value of that next pixel compared to the previous adjacent pixel.If that difference value is still greater than the same preselectedlevel, that process continues in that same direction until thedifference value does not exceed the preselected level. Once the pixelwhere the difference value does not exceed the preselected value isdetermined, that pixel is considered to be the extent of the defect, oron the edge of the defect, in that direction. The same procedure isperformed in other selected directions to similarly find the extent, oredge of the defect, in each of those directions. This effectivelydefines the edge of the defect, or, since the pixels are square,substantially a box around the defect. How many directions in which thecomparisons are performed is optional and may be partly dependent onprior knowledge as to the approximate location of the defect relative toother features on the reticle (e.g., proximity to a region of theopposite polarity such as a trace and an opaque region, corner of anopaque or transparent region) of the accuracy to which the extent of thedefect is to be determined (e.g., it may be desirable to perform thesame function diagonally outward from the center of the defect, orperhaps radially every 10°).

[0036]FIG. 5 illustrates, as a bell shaped curve 48, how the gray scalevalues of the individual pixels of a defect might vary with distancefrom the gray scale value of the pixel at the fine center, F, of thedefect along one axis. Thus, to determine the extent of the defect thegray scale value of adjacent pixels are compared with each other untilthe difference in gray scale values between two adjacent pixel along thesame axis from the center pixel, F, is below a preselected thresholdvalue. Using the values shown in FIG. 5 and assuming that the thresholdvalue is 2, the pixel at location 50 will represent the extent of thedefect to the left of the defect center since there is only a differenceof 1 with the gray scale value of the next pixel to the right, whereasthe differences between all other pixels between pixel 50 and the centerpixel are all greater than 2. As stated above, this technique is used inas many other directions as desired to find the extent of the defect inthe pixel grid image 34.

[0037] Back to FIG. 1, with the extent of the defect determined it isnow possible to determine the transmittible energy level of the defect(26). First, the pixel energy of the defect is determined by summing allgray scale values of all of the pixels that are encompassed by theextent of the defect in each direction considered above. Second, inorder to measure the energy difference provided by the defect alone, itis necessary to subtract an approximation of the background energy valuethat would have been present had there not been a defect, or in otherwords the background noise of this region of the reticle image. Avariation in the transmittible energy level of a defect could resultfrom areas that are totally transparent, to those that are somewhattranslucent, to those that are totally opaque. The causation for thosetypes of variations in transmittible energy level are numerous. Perhapsthe chrome layer on the reticle is thinner in some locations, perhapsthere is a scratch that extends substantially through, or all the waythrough, the chrome layer, perhaps there is a chemical stain on thetransparent or opaque regions on the reticle that may or may not impedethe transmission of light through the transparent regions . . . the listis virtually endless.

[0038] One way to approximate the background energy of the defect is tosum together the gray scale values for all of the pixels in animmediately adjacent region to the pixel grid image (see 12 above) thatis the same size and shape as the determined extent of the defect. Forbest results, this immediately adjacent region should be defect free,and of the same polarity as the defect. The summed energy from thatadjacent region is then considered to be approximately what would havebeen the background energy level of the defect region and is thereforesubtracted from the summed energy level of the defect region to get amore accurate measure of the transmittible energy level of the defectregion.

[0039] To obtain a more accurate approximation of the background energyof the defect region, multiple adjacent regions of the same size andshape can be used with the energy levels of those regions averagedtogether. Then that averaged energy value would be subtracted from theenergy value of the defect region. Through the use of the average level,the effects of some anomalies or system noise in the regions being usedto determine the background energy level would be reduced.

[0040]FIG. 6 illustrates the pixel grid image 34 for the defect ofinterest with the extent of that defect shown by outline 52. First thetotal of the gray scale values for all pixels within that defined defectextent are summed together. Then an area of the same size and shape 54is considered adjacent to the extent of the defined defect with the grayscale values of all of the pixels within that area added together todetermine an approximation of the background gray scale energy value forthe defined defect area 52. The value for area 54 is then subtractedfrom the value of defect area 52 to determine the actual level oftransmittible energy level of defect area 52. Alternatively, asdiscussed above, multiple adjacent areas 54, 56 and 58, of the same sizeand shape can also be defined adjacent to defect area 52 with the totalgray scale energy level. for all of the pixels within those areas addedtogether and the total then divided by 3 in this example to determine anaverage background energy level to be subtracted from the energy levelof defect area 52.

[0041] Referring to FIG. 1, it is also known that the proximity of adefect in a reticle to an edge in the pattern on the reticle can have anamplified effect on the printing of the defect to the substrate. It isnecessary to then determine that proximity, if it exists. The proximityof a defect to a pattern edge on a reticle (28) is then determined bysearching in numerous directions outside the determined extent of thedefect for a gradient (geometry edge) where the gray scale value rapidlyapproaches the opposite polarity of the defect region. Linear sub-pixelinterpolation is then used to determine the 50% point of the gradient(i.e., where the gray scale value is one half the difference in themaximum gray scale levels on each side of that pixel located at thepoint of transition). With the transition pixel location determined, thedistance between the transition pixel and the center pixel of the defectin microns is the distance to the reticle edge from the defect.

[0042]FIG. 7a illustrates the typical gray scale values of pixels thatform the edge of a line on a reticle. In this example pixels P₁, P₂, P₃and P₄ are shown, respectively, as having a relative gray scale value ofa few percent, 30%, 68% and 100%. Further, as stated above, the locationof the edge of a line is defined as where the relative gray scale valueis 50%. Since there is no pixel that has the 50% value, linear sub-pixelinterpolation is used to determine a close approximation to thatlocation. In this example it can be seen that location is somewherebetween the centers of pixels P₂ and P₃. In FIG. 7b the portion of thecurve that includes the relative values and spacing of pixels P₂ and P₃are shown with a straight line drawn between those two points on thecurve. Thus, since the relative values for those points are 68% and 30%,a difference of 38, and the difference of 50% from 68% is 18, thelocation of the 50% point will be {fraction (18/38)} ({fraction (9/19)}) of a pixel width from the center of pixel P₃ to the center of pixelP₂. Thus, the distance from the line edge to the defect center pixel, F,is the distance from the defect center pixel, F, to the center of pixelP₂ plus {fraction (9/18)} of a pixel width.

[0043] As stated above, (see FIG. 1) other factors contribute (30) towhether a defect on a reticle prints onto a substrate (e.g., type ofresist, type of stepper, illumination frequency, etc.) with differentweighting factors being assignable for each of those variables once itis known what chemicals and equipment a manufacturer uses. Thus,isolated defect printability is predicted by applying selected weightingto the energy of the defect where those weighting factors areattributable to a particular wafer fab process. Similarly, near edgedefect printability is also determined by both that distance and theparticular wafer fab process that is used. Thus, other weighting factorsmust be applied to the energy level of the defect to predictprintability of those defects that are near an edge. There are thereforetwo factors that work together to determine the near edge weightingfactor to use: how close a defect is to an edge with a higher weightingvalue necessary the closer the defect is to the edge; and the particularwafer fab process being used.

[0044] It should be noted that the above discussion has been for asingle defect, and it should further be understood that for multipledefects that may be found in a reticle the above described procedurewould be repeated for each such defect that was not otherwiseincorporated into the defect extent of an earlier processed defect.

[0045] It should further be noted that the above discussion has includeda group of procedures, with some of those procedures being optimizationprocedures, and that if some of those procedures are not performed,improvement over the prior art will still be achieved. For example,those procedures corresponding to blocks 20, 22, 28 and 32 are secondaryprocedures that can be omitted with a useful result still beingachieved.

[0046] While the present invention has been described having severaloptional steps, it is contemplated that persons skilled in the art, uponreading the preceding descriptions and studying the drawings, willrealize various alternative approaches to the implementation of thepresent invention, including several other optional steps, orconsolidations of steps. It is therefore intended that the followingappended claims be interpreted as including all such alterations andmodifications that fall within the true spirit and scope of the presentinvention.

What is claimed is:
 1. A computer program stored on a computer-readablemedium for determining the printability of a defect on a reticle orphotomask onto a substrate during processing of said substrate, saidprintability being determined from a defect review menu of said reticleor photomask prepared by an inspection machine and weighting factorsrelated to a fabrication procedure used to produce said substrate, saidcomputer program comprising: a. instructions for creating a pixel gridimage of a portion of said reticle or photomask containing said defectidentified in said defect review menu, said pixel grid image having aplurality of associated individual pixel images of said reticle orphotomask; b. instructions for assigning a gray scale value to each ofsaid associated individual pixel images of said pixel grid image; c.instructions for selecting a probable center pixel of said defect insaid pixel grid image; d. instructions for determining a polarity ofsaid defect; e. instructions for determining a region of physical extentof said defect; and f. instructions for determining a transmissivityenergy level of said region of physical extent of said defect.
 2. Thecomputer program of claim 1 wherein said gray scale values have a rangefrom 0 to 256, with 0 representing an opaque pixel and 256 representinga totally transmissive pixel.
 3. The computer program of claim 1wherein: instructions c. include: g. instructions for noting coordinatesof said probable center pixel from said defect review menu; andinstructions d. include: h. instructions for selecting a reference pixelfrom said defect review menu with said reference pixel spaced-apart fromsaid probable center pixel and not included in said region of physicalextent of said defect; i. instructions for assigning a gray scale valueto said reference pixel; j. instructions for comparing said gray scalevalue of said reference pixel with said gray scale value of saidprobable center pixel; and k. instructions for assigning a polarity ofwhite to said region of physical extent of said defect if said grayscale value of said probable center pixel is greater than said grayscale value of said reference pixel, or a polarity of black to saidregion of physical extent of said defect if said gray scale value ofsaid probable center pixel is less than said gray scale value of saidreference pixel.
 4. The computer program of claim 1 wherein:instructions c. include: g. instructions for noting coordinates of saidprobable center pixel from said defect review menu; and instructions d.include: h. instructions for selecting a plurality of reference pixelsfrom said defect review menu with each of said plurality of referencepixels spaced progressively further apart from said probable centerpixel in the same direction; i. instructions for assigning a gray scalevalue to each of said plurality of reference pixels; instructions forcomparing said gray scale value of each of said plurality of saidreference pixels with said gray scale value of said probable centerpixel, and said gray scale value of each reference pixel and each otherreference pixel adjacent thereto; and k. instructions for assigning apolarity of white to said region of physical extent of said defect ifsaid gray scale value of each of said plurality of reference pixelssuccessively decreases from said gray scale value of said probablecenter pixel as the spacing from said probable center pixel increases;or a polarity of black to said region of physical extent of said defectif said gray scale value of each of said plurality of reference pixelssuccessively increases from said gray scale value of said probablecenter pixel as the spacing from said probable center pixel increases;or if the difference between said gray scale value of said probablecenter pixel and each of said plurality of references pixels varies inone direction and then in an opposite direction the further from saidprobable center pixel said reference pixel is located, said probablecenter pixel is probably located in close proximity to a line edge onsaid reticle or photomask requiring that said plurality of referencespixels be reselected in a different direction from said probable centerpixel in order to determine polarity of said region of physical extentof said defect and steps h., i. and j. repeated until a polaritydetermination for said region of physical extent of said defect can bemade.
 5. The computer program of claim 1 wherein instructions e.include: g. instructions for selecting a minimum threshold value of adifference in gray scale values between adjacent pixels to define anedge of said region of physical extent of said defect; h. instructionsfor noting said gray scale value for said probable center pixel of saiddefect; i. instructions for selecting a direction beginning with saidprobable center pixel in which to search for said edge of said region ofphysical extent of said defect; j. instructions for calculating adifference in gray scale values of juxtaposed pixels in said selecteddirection starting with said probable center pixel until the magnitudeof said difference in gray scale values first exceeds said threshold; k.instructions for setting said edge of said region of physical extent ofsaid defect in the selected direction as a boundary between saidjuxtaposed pixels where said threshold level is exceeded; and l.repeating instructions i. through k. in numerous selected directionsfrom said probable center pixel to define said physical extent of saiddefect in said selected directions.
 6. The computer program of claim 1wherein instructions f. include: g. instructions for summing togethersaid gray scale values of all of is said pixels included within saidphysical extent of said defect to determine an initial measure of anenergy level of said defect; and h. instructions for subtracting abackground energy level from said initial measure of an energy level todetermine said transmissivity energy level of said region of physicalextent of said defect.
 7. The computer program of claim 6 whereininstructions h. include: i. instructions for selecting a region adjacentsaid region of physical extent of said defect on said reticle orphotomask having the same size and shape as said region of physicalextent of said defect; j. instructions for summing together gray scalevalues of all pixels included within said adjacent region to determine abackground energy level of said reticle or photomask; and k.instructions for subtracting said background energy level from saidinitial measure of an energy level to determine said transmissivityenergy level of said region of physical extent of said defect.
 8. Thecomputer program of claim 7 wherein said adjacent region of instructionsi. is defect free.
 9. The computer program of claim 6 whereininstructions h. include: i. instructions for selecting a plurality ofregions adjacent said region of physical extent of said defect on saidreticle or photomask, each selected region having the same size andshape as said region of physical extent of said defect; j. instructionsfor summing together gray scale values of all pixels included withineach of said plurality of adjacent regions separately; k. instructionsfor averaging together each of said gray scale value sums to determine abackground energy level of said reticle or photomask; and l.instructions for subtracting said background energy level from saidinitial measure of an energy level to determine said transmissivityenergy level of said region of physical extent of said defect.
 10. Thecomputer program of claim 1 further includes: g. instructions fordetermining printability of said defect by applying a weighting factorto said transmissivity energy level, said weighting factor being acombination of several variables contributed by a particular waferfabrication process being used to produce a substrate using said reticleor photomask.
 11. The computer program of claim 1 between instructionsd. and e. further includes: g. instructions for determining a coarsecenter pixel of said defect using said probable center defect and saidpolarity of said defect.
 12. The computer program of claim 1 whereininstructions g. include: h. instructions for comparing said gray scalevalue of said probable center pixel individually with said gray scale ofeach pixel juxtaposed to said probable center pixel; i. instructions fordetermining if said polarity of said defect is white and step h. revealsa pixel juxtaposed to said probable center pixel that has a higher grayscale value than said gray scale value of said probable center pixel,said juxtaposed pixel is selected as said coarse center pixel of saiddefect; j. instructions for determining if said polarity of said pixelgrid image is black and step h. reveals a pixel juxtaposed to saidprobable center pixel that has a lower gray scale value than said grayscale value of said probable center pixel, said juxtaposed pixel isselected as said coarse center pixel of said defect; k. instructions forrepeating instructions h. through j. if instructions i. or j. resultedin the selection of a different coarse center pixel; and l. instructionsfor selecting a last selected coarse center pixel as said coarse centerpixel following the last performance of instructions k., or selectingsaid probable center pixel as said coarse center pixel if an initialperformance of neither instructions i. nor j. resulted in the selectionof a different coarse center pixel.
 13. The computer program of claim 11wherein instructions e. include: h. instructions for selecting a minimumthreshold value of a difference in gray scale values between adjacentpixels to define an edge of said region of physical extent of saiddefect; i. instructions for noting said gray scale value for said coarsecenter pixel of said defect; j. instructions for selecting a directionbeginning with said coarse center pixel in which to search for said edgeof said region of physical extent of said defect; k. instructions forcalculating a difference in gray scale values of juxtaposed pixels insaid direction selected in step j. starting with said coarse centerpixel until the magnitude of said difference in gray scale values firstexceeds said threshold; l. instructions for setting said edge of saidregion of physical extent of said defect in the direction selected ininstructions j. as a boundary between said juxtaposed pixels identifiedin instructions k. where said threshold level is exceeded; and m.instructions for repeating instructions j. through
 1. in numerousselected directions from said coarse center pixel to define saidphysical extent of said defect in said selected directions.
 14. Thecomputer program of claim 11 between instructions g. and e. includes: h.instructions for determining a fine center of said defect using saidcoarse center pixel and said polarity of said defect.
 15. The computerprogram of claim 14 wherein: instructions g. include: i. instructionsfor comparing said gray scale value of said probable center pixelindividually with said gray scale of each pixel juxtaposed to saidprobable center pixel; j. instructions for determining if said polarityof said defect is white and instructions i. reveal a pixel juxtaposed tosaid probable center pixel that has a higher gray scale value than saidgray scale value of said probable center pixel, said juxtaposed pixel isselected as said coarse center pixel of said defect; k. instructions fordetermining if said polarity of said pixel grid image is black andinstructions i. reveal a pixel juxtaposed to said probable center pixelthat has a lower gray scale value than said gray scale value of saidprobable center pixel, said juxtaposed pixel is selected as said coarsecenter pixel of said defect; l. instructions for repeating instructionsi. through k. if instructions j. or k. resulted in the selection of adifferent coarse center pixel; and m. instructions for selecting a lastselected coarse center pixel as said coarse center pixel following thelast performance of instructions l., or selecting said probable centerpixel as said last coarse center pixel if an initial performance ofneither instructions j. nor k. resulted in the selection of a coarsecenter pixel; and instructions h. include: n. instructions fordetermining a fine center of said defect using a subpixel interpretationroutine on said coarse center pixel.
 16. The computer program of claim15 wherein instructions n. include: o. instructions for selecting saidcoarse center pixel and a first and a second pixel each juxtaposed, andon opposite sides of, said coarse center pixel, with said three pixelsdefining a first straight line; p. instructions for summing said grayscale values of each of said coarse center pixel and said first andsecond juxtaposed pixels; q. instructions for summing said gray scalevalue of said first juxtaposed pixel with twice said gray scale value ofsaid coarse center pixel and with three times said gray scale value ofsaid second juxtaposed pixel; r. instructions for dividing a result ofinstructions q. by a result of instructions p. to yield a value having awhole number portion and a fractional number portion, wherein if saidwhole number portion is 1 said fine center of said defect isspaced-apart from said coarse center pixel toward said first juxtaposedpixel by said fractional number portion of a pixel width along saidfirst straight line, and wherein if said whole number portion is 2 saidfine center of said defect is spaced-apart from said coarse center pixeltoward said second juxtaposed pixel by said fractional number portion ofa pixel width along said first straight line; s. instructions forselecting said coarse center pixel and a third and a fourth pixel eachjuxtaposed, and on opposite sides of, said coarse center pixel, withsaid three pixels defining a second straight line; t. instructions forsumming said gray scale values of each of said coarse center pixel andsaid third and fourth juxtaposed pixels; u. instructions for summingsaid gray scale value of said third juxtaposed pixel with twice saidgray scale value of said coarse center pixel and with three times saidgray scale value of said fourth juxtaposed pixel; v. instructions fordividing a result of instructions u. by a result of instructions t. toyield a value having a whole number portion and a fractional numberportion, wherein if said whole number portion is 1 said fine center ofsaid defect is spaced-apart from said coarse center pixel and said thirdjuxtaposed pixel by said fractional number portion of a pixel widthalong said second straight line, and wherein if said whole numberportion is 2 said fine center of said defect is spaced-apart from saidcoarse center pixel and said fourth juxtaposed pixel by said fractionalnumber portion of a pixel width along said second straight line; and w.instructions for determining a point of intersection between said firstand second straight lines with said point of intersection being saidfine center of said defect on said reticle or photomask.
 17. Thecomputer program of claim 14 wherein instructions e. include: i.instructions for selecting a minimum threshold value of a difference ingray scale values between adjacent pixels to define an edge of saidregion of physical extent of said defect; j. instructions for notingsaid gray scale value for a pixel in which said fine center of saiddefect is located; k. instructions for selecting a direction beginningwith said fine center of said defect in which to search for said edge ofsaid region of physical extent of said defect; l. instructions forcalculating a difference in gray scale values of juxtaposed pixels insaid direction selected in step k. starting with said pixel in whichsaid fine center of said defect is located until the magnitude of saiddifference in gray scale values first exceeds said threshold; m.instructions for setting said edge of said region of physical extent ofsaid defect in the direction selected in step k. as a boundary betweensaid juxtaposed pixels identified in step l. where said threshold levelis exceeded; and n. instructions for repeating instructions k. throughm. in numerous directions from said pixel in which said fine center ofsaid defect is located to define said physical extent of said defect insaid selected directions.
 18. The computer program of claim 1 furtherincludes: g. instructions for determining proximity of said defect to anedge of pattern on said reticle or photomask using said region ofphysical extent said defect nd said polarity of said defect.
 19. Thecomputer program of claim 18 wherein instructions g. include: h.instructions for searching said defect review menu of said reticle orphotomask in a selected direction outside said region of physical extentof said defect for pixels having a gradient of gray scale values thatsuccessively and rapidly approach an opposite polarity from that of saiddefect; i. instructions for determining a difference of gray scalevalues of said gradient between pixels having the greatest and leastgray scale values; j. instructions for performing sub-pixelinterpolation on pixels defining said gradient to determine a transitionpixel location where said gradient has a gray scale value half-waybetween said greatest and least gray scale values of said gradient withsaid location being a point on an edge of said pattern on said reticleor photomask; and k. instructions for measuring a distance between saidpoint of an edge and said probable center pixel with said measureddistance being a distance from said edge of said pattern on said reticleor photomask and said defect in said selected direction.
 20. Thecomputer program of claim 19 further includes: l. instructions forrepeating instructions h. through k. for additional directions outsidesaid region of physical extent of said defect to determine proximity ofsaid defect to additional points on edges on said reticle or photomask.21. The computer program of claim 18 further includes: h. instructionsfor selecting a threshold transmissivity level above which said defectis deemed printable; i. instructions for determining a primary weightingfactor from said region of physical extent of said defect and severalvariables of a particular wafer fabrication process being used toproduce said substrate; j. instructions for determining a secondaryweighting factor based on said proximity of said defect to a point on anedge of a pattern on said reticle or photomask; k. instructions forcombining said primary weighting factor and said secondary weightingfactor; l. instructions for applying said combined weighting factors tosaid transmissivity energy level to determine an effectivetransmissivity energy level of said defect; and m. instructions forcomparing said effective transmissivity energy level to said thresholdtransmissivity level with said defect being printable if said effectivetransmissivity energy level exceeds said threshold transmissivity level.22. The computer program of claim 21 wherein said secondary weightingfactor is selected to produce an effective transmissivity energy levelthat is higher the closer said defect is to a point on an edge of apattern on said reticle or photomask as opposed to defects that are notin close proximity to an edge on said reticle or photomask.
 23. Acomputer program stored on a computer-readable medium for determiningthe printability of a defect on a reticle or photomask onto a substrateduring processing of said substrate, said printability being determinedfrom a defect review menu of said reticle or photomask prepared by aninspection machine and weighting factors related to a fabricationprocess used to produce said substrate, said computer programcomprising: a. instructions for creating a pixel grid image of a portionof said reticle or photomask containing said defect identified in saiddefect review menu, said pixel grid image having a plurality ofassociated individual pixel images of said reticle or photomask; b.instructions for assigning a gray scale value to each of said associatedindividual pixel images of said pixel grid image; c. instructions forselecting a probable center pixel of said defect in said pixel gridimage; d. instructions for determining a polarity of said defect; e.instructions for determining a coarse center pixel of said defect usingsaid probable center defect from and said polarity of said defect; f.instructions for determining a fine center of said defect using saidcoarse center pixel and said polarity of said defect; e. instructionsfor determining a region of physical extent of said defect; f.instructions for determining a transmissivity energy level of saidregion of physical extent of said defect; g. instructions fordetermining proximity of said defect to an edge of a pattern on saidreticle or photomask using said region of physical extent of said defectand said polarity of said defect; and h. instructions for determiningprintability of said defect by applying a weighting factor to saidtransmissivity energy level, said weighting factor being a combinationof several variables contributed by a particular wafer fabricationprocess being used to produce said substrate using said reticle orphotomask.
 24. The computer program of claim 23 wherein instructions h.include: i. instructions for selecting a threshold transmissivity levelabove which said defect is deemed printable; j. instructions fordetermining a primary weighting factor from said region of physicalextent of said defect and several variables of a particular waferfabrication process being used to produce said substrate; k.instructions for determining a secondary weighting factor based on saidproximity of said defect to an edge of a pattern on said reticle orphotomask; l. instructions for combining said primary weighting factorand said secondary weighting factor; m. instructions for applying saidcombined weighting factors to said transmissivity energy level todetermine an effective transmissivity energy level of said defect; andn. instructions for comparing said effective transmissivity energy levelto said threshold transmissivity level with said defect being printableif said effective transmissivity energy level exceeds said thresholdtransmissivity level.
 25. The computer program of claim 24 wherein saidsecondary weighting factor is selected to produce an effectivetransmissivity energy level that is higher the closer said defect is toa point on an edge of a pattern on said reticle or photomask as opposedto defects that are not in close proximity to an edge on said reticle orphotomask.